1. Field of the Invention
This invention relates to an alginate oligosaccharide such as calcium alginate oligosaccharide or potassium alginate oligosaccharide, more particularly, an alginate oligosaccharide having an antihypertensive action and a method for producing the same.
The present invention further relates to an anti-hypertensive food containing the above-mentioned alginate oligosaccharide.
2. Description of the Prior Art
Seaweeds have been generally used as everyday foodstuffs and thought to be effective in maintaining the health and preventing hypertension and aging for a long time. It is known that brown algae such as sea tangle, from among the seaweeds, particularly contribute to the reduction of blood pressure thanks to the actions of alginic and amino acids contained therein.
However it is generally difficult in our daily diet to continuously take a large amount of seaweeds.
Therefore, it is desirable to make seaweeds easy to take by, for example, adding processed products of seaweeds to foods.
Alginic acid (potassium alginate or sodium alginate), which is a major intercellular mucopolysaccharide contained in brown algae, comprises D-mannuronic acid and L-guluronic acid as its major constituting molecules. It is considered that alginate oligosaccharides can be obtained by lowering the molecular weight of this alginic acid.
However, it is known that alginic acid is very hardly decomposable, since an aqueous solution of alginic acid is highly viscous and the alginic acid forms a metal salt together with, for example, calcium contained in said aqueous solution and thus sets to gel.
Regarding treatments of alginic acid, attempts have been made to decompose this substance by using an alginate lyase produced by a microorganism. There have been reported various examples of such a lyase on a laboratory level.
The oligosaccharides obtained by using the above-mentioned lyase include sodium alginate oligosaccharide and potassium alginate oligosaccharide. The potassium alginate oligosaccharide contains a large amount of sodium in addition to potassium, seemingly due to the purity of the potassium alginate of the polysaccharides employed as a starting material. On the other hand, there has been provided no report on the calcium alginate oligosaccharide. Further, there has been reported neither any physiological activity such as an antihypertensive action of these oligosaccharides nor any application of them to foods.